This study will asess whether INH is handled and removed from the body differently in persons with advanced Hiv compared to controls. The pharmacokinetic disposition of INH and it acetylated metabolite will be dtermined from blood samples collected for 12 hours after a dose of INH. Subjects will drink a can of cola and the ratio of acetylated to nonacetylated caffeine in a subsequent spot of urine sample will be used in this pilot to provide information about differences in the absorption and metabolism of persons with AIDS.